1. Field of the Invention
This invention relates to Raney copper, to a process for the production thereof and to a process for dehydrogenating alcohols.
2. Background Information
It is known to dehydrogenate diethanolamine to yield iminodiacetic acid (U.S. Pat. No. 5,689,000; WO 96/01146; WO 92/06949; published patent application JP 091 55 195; U.S. Pat. No. 5,292,936; U.S. Pat. No. 5,367,112; CA 212 10 20).
The present invention provides Raney copper which is characterised in that it is doped with at least one metal from the group comprising iron and/or noble metal.
Doping may be achieved both by alloying the doping element with the Raney alloy, which consists of copper and aluminium, and by impregnating the previously prepared Raney copper with the doping element.
The Raney copper according to the invention may contain the doping elements in a quantity of 10 ppm to 5 wt. %. Noble metal doping may amount to 10 to 50000 ppm, preferably 500 to 50000 ppm. The doping metals may be selected from the group comprising iron and palladium, platinum, gold, rhenium, silver, iridium, ruthenium and/or rhodium.
The Raney copper according to the invention may comprise meso- and macropores, but no micropores.
The inital formed alloy can contain more than 50% Cu so that the finished catalyst contains more residual Al than normally found under the same activation conditions.
The initial formed alloy can be heat treated in air temperatures higher than 500xc2x0 C. activation.
The initial formed alloy can contain more than 50% Cu and heat treated in air temperatures higher than 500xc2x0 C. before activation.
The average particle size of the Raney copper according to the invention may be 35xc2x130 xcexcm.
The average particle size of the Raney copper according to the invention is of significance during use in oxidation reactions or alcohol dehydrogenation reactions.
On repeated use, known Raney copper forms granules (agglomerates), so deactivating the Raney copper.
The Raney copper according to the invention doped with iron and/or noble metal is not deactivated by unwanted granulation. Advantageously, the Raney copper according to the invention may readily be filtered.
The Raney copper according to the invention exhibits greater activity in the dehydrogenation of ethylene glycol than the Cr/Raney copper according to EP 0 620 209 A1 or U.S. Pat. No. 5,292,936.
The Raney copper according to the invention furthermore advantageously contains no toxic metals, such as chromium for example.
The present invention also provides a process for the production of the Raney copper, which process is characterised in that a copper/aluminium alloy is activated by means of an aqueous sodium hydroxide solution, the catalyst is washed, suspended in water, an iron salt or noble metal salt solution is added to this suspension, the pH value of the solution is adjusted to a value from 4 to 11, the catalyst is separated from the solution and washed.
The present invention also provides a process for the production of the Raney copper, which process is characterised in that the doping metal is alloyed together with copper and aluminium, is then activated by means of aqueous sodium hydroxide solution and the catalyst is washed.
The present invention also provides a process for the catalytic dehydrogenation of alcohols to their corresponding carbonyls and carboxylic acids, which process is characterised in that a Raney copper doped with iron or noble metal is used as the catalyst.
The process according to the invention for the dehydrogenation of alcohols may be used for dehydrogenating glycols and/or aminoalcohols. The catalyst may be used in the form of a suspension for such reactions.
The alcohols which may be dehydrogenated according to the invention may be mono- or polyhydric alcohols. Said alcohols, including polyether glycols, may be aliphatic, cyclic or aromatic compounds which react with a strong base to yield the carboxylate.
It is necessary in this connection that the alcohol and the resultant carboxylate are stable in a strongly basic solution and that the alcohol is at least somewhat soluble in water.
Suitable primary, monohydric alcohols may include:
aliphatic alcohols, which may be branched, linear, cyclic or aromatic alcohols, such as for example benzyl alcohol, wherein these alcohols may be substituted with various groups which are stable in bases.
Suitable aliphatic alcohols may be ethanol, propanol, butanol, pentanol or the like.
According to the invention, glycols may be oxidised or dehydrogenated to yield carboxylic acids. Glycols may, for example, be:
ethylene glycol
propylene glycol
1,3-propanediol
butylene glycol
1,4-butanediol
It is thus possible, for example, to dehydrogenate ethylene is glycol to yield glycolic acid (monocarboxylic acid) and to produce the dicarboxylic acid oxalic acid by subsequent reaction with KOH.
Aminoalcohols may also be dehydrogenated with the doped Raney copper according to the invention to yield the corresponding aminocarboxylic acids. The amino alcohols may have 1 to 50 C atoms.
It is accordingly possible, for example, to dehydrogenate N-methylethanolamine to yield sarcosine; THEEDA (tetrahydroxyethylethylenediamine) to yield the tetrasodium salt of EDTA (ethylenediaminetetraacetate); monoethanolamine to yield glycine; diethanolamine to yield iminodiacetic acid; 3-amino-1-propanol to yield beta-alanine; 2-amino-1-butanol to yield 2-aminobutyric acid.
In one embodiment of the invention, the process according to the invention may be used to dehydrogenate aminoalcohols of the formula 
in which R1 and R2 each mean hydrogen; hydroxyethyl; xe2x80x94CH2CO2H; an alkyl group having 1 to 18 C atoms; an aminoalkyl group having 1 to 3 C atoms; a hydroxyalkylaminoalkyl group having 2 to 3 C atoms and phosphonomethyl.
The aminoalcohols which may be used according to the invention are known. If R1 and R2 are hydrogen, the aminoalcohol is diethanolamine.
If R1 and R2 are hydroxyethyl, the aminoalcohol is triethanolamine. The resultant aminocarboxylic acid salts of these starting aminoalcohols should be the salts of glycine, iminodiacetic acid and nitrilotriacetic acid respectively. Further aminoalcohols comprise N-methylethanolamine, N,N-dimethylethanolamine, N-ethylethanolamine, N-isopropylethanolamine, N-butylethanolamine, N-nonylethanolamine, N-(2-aminoethyl)ethanolamine, N-(3-aminopropyl)ethanolamine, N,N-diethylethanolamine, N,N-dibutylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-isopropyldiethanolamine, N-butyldiethanolamine, N-ethyl-N-(2-aminoethyl)-ethanolamine, N-methyl-N-(3-aminopropyl)ethanolamine, tetra(2-hydroxyethyl)ethylenediamine and the like.
Further examples of aminocarboxylic acid salts are the salts of N-methylglycine, N,N-dimethylglycine, N-ethylglycine, N-isopropylglycine, N-butylglycine, N-nonylglycine, N-(2-aminoethyl)glycine, N-(3-aminopropyl) glycine, N,N-diethylglycine, N,N-dibutylglycine, N-methyliminodiacetic acid, N-ethyliminodiacetic acid, N-isopropyliminodiacetic acid, N-butyliminodiacetic acid, N-ethyl-N-(2-aminoethyl)glycine, N-methyl-N-(3-aminopropyl)glycine, ethylenediaminetetraacetic acid etc.
R1 or R2 may also be a phosphonomethyl group, wherein the starting amino compound may be N-phosphonomethylethanolamine and the resultant amino acid N-phosphonomethylglycine. If, of R1 or R2, one R=phosphonomethyl and the other R=xe2x80x94CH2CH2OH, the resultant amino acid would be N-phosphonomethyliminodiacetic acid, which may be converted in known manner into N-phosphonomethylglycine. If, of R1 or R2, one R=phosphonomethyl and the other R is an alkyl group, the resultant acid would be N-alkyl-N-phosphonomethylglycine, which may be converted into N-phosphonomethylglycine in accordance with U.S. Pat. No. 5,068,404.
The process according to the invention may be performed at is a temperature of 50 to 250xc2x0 C., preferably of 80 to 200xc2x0 C., and at a pressure of 0.1 to 200 bar, preferably at standard pressure to 50 bar.
The pressure is required because the alcohols have an elevated vapour pressure. If the pressure were too low, the alcohol would also be discharged when the hydrogen was discharged.